Five of Shell's oil flow platforms are now closed
Nigerian troops have been sent to the troubled oil town of Warri following the death of 10 people in clashes between youths and the security forces.
Oil giant Shell has temporarily shut more production facilities in the volatile Niger Delta region following the insecurity.
Shell has now closed three more oil flow stations in the region - bringing the total to five - reducing output by 76,000 barrels a day.
This follows violent clashes between Nigerian navy troops and ethnic Ijaw militants at the village of Okerenkoko on the Escravos River.
The village is close to the oil port of Warri, where Shell and other multinational oil firms are based.
Army spokesman, Colonel Onwuamaegbu Chukuemeka told the French news agency, AFP: "I am aware that soldiers have been sent in. But I don't have the details yet.
Shell's Nigerian subsidiary has also evacuated employees "who are not vital to operations" from company facilities in the area, a spokesman said.
One staff member is still unaccounted for.
Activists from the Federated Niger Delta Ijaw Communities accused the navy of provoking the hostilities by launching a premeditated attack on the village last Thursday.
The soldiers accused the community of planning to disrupt oil facilities and attack rival communities, the activists said in a statement.
The Ijaw claim their fishing communities have been polluted by the oil industry.
They demand compensation and investment in local infrastructure from the oil giants.
The approach of next month's national elections, the first since Nigeria's return to civilian rule, has also heightened tensions in the area.
A Shell spokesman said the dispute had nothing to do with the company's operations in Nigeria.
Marine operations on the two rivers in the region have also been suspended.